DE 10 2009 047 861 discloses a high-pressure discharge lamp with a discharge vessel, in which a starting aid is used at the end of the discharge vessel.
Free electrons must be produced in the discharge vessel for starting high-pressure discharge lamps. Until now, this has been achieved by radioactive krypton-85 in the fill gas.
Gas discharge lamps without any radioactivity in the fill gas can start markedly more reliably when starting aids are used. If the lamp geometry does not permit an additional light source such as a UV enhancer, sometimes a discharge in an outer bulb can be used as UV light source; see U.S. 2003034738, WO2008007284. By suitably selecting the gas in the outer bulb, the outer bulb discharge usually has a lower starting voltage than the lamp. However, these voltages are still higher than the starting voltages of lamps filled with radioactive krypton-85.